Methods for exposing photographic materials include known image forming methods using a scanner system wherein the original is scanned and a silver halide photographic material is exposed on the basis of the resulting image signals to form a negative or positive image corresponding to the image of the original. Although there are a variety of recording devices utilizing image forming methods employing a scanner system, any dot generator systems using dot generators are used at present.
Glow lamps, xenon lamps, mercury vapor lamps, tungsten lamps and light-emitting diodes have been conventionally used as light sources for recording in these scanner system recording devices.
However, these light sources have practical disadvantages because the output thereof is low and the working life thereof is short. To solve these problems, scanners using, as light sources for the scanner system, coherent laser light sources such as Ne-He lasers; argon lasers, He-Cd lasers and semiconductor lasers have been developed.
Many scanners use an argon laser as the light source thereof because of high output and because the laser beam can be closely stopped down.
Light-sensitive materials having high sensitivity are advantageous in stopping down output to achieve a long working life of the laser bulb, although argon laser provides a high output. Further, a laser beam must be shaped using a slit, etc. to obtain good dots, and light-sensitive materials having high sensitivity are required for coping with laser output which is reduced as a result.
To provide light-sensitive materials for laser beam, a called spectral sensitization technique is generally used wherein a sensitizing dye having absorption at about 488 nm is employed to achieve sensitivity to light having a wavelength of 488 nm, the wavelength of light of a laser beam. The light-sensitive materials, after processing retain a residual color caused by the sensitizing dye, and the commercial value of the finished products is reduced.
An increase in the working efficiency and a speed up of operations in the printing industry has been required recently. In particular, there are requirements to speed-up scanning and to shorten the processing time for the light-sensitive materials.
In order to meet the needs of the printing industry, a speed-up of scanning of the exposure devices (scanner, plotter) and an increase in screen ruling or beams stopped down to obtain an image of higher quality is required. The silver halide photographic materials must have high sensitivity, must have excellent processing stability and must be capable of being rapidly processed. However, when the photographic materials are rapidly processed, residual color caused by sensitizing dyes after processing occurs and this is a problem.
The term "rapid development" or "rapid processing" as used herein refers to processing which takes 15 to 60 seconds for "the leading edge of a film to pass through a developing bath, a transfer zone, a fixing bath, a transfer zone, a rinse bath and a drying zone and emerge from the drying zone in an automatic processor".
Spectral sensitization is an important technique as a means for broadening the spectral sensitivity of silver halide photographic emulsions form the intrinsic sensitivity region of silver halide to a longer wavelength side. The sensitive wavelength region can be controlled into the infrared region almost at will by choosing the structures of the sensitizing dyes used for this purpose. However, various disadvantages still exist, and improvements are required. When the sensitizing dyes are applied to the silver halide emulsion, the objects are (1) that the spectral sensitivity distribution is proper and (2) that high sensitivity can be achieved in the desired spectral sensitivity region, and undesirable phenomena do not occur, for example, (a) fogging does not occur, (b) a change in sensitivity and an increase in fog do not occur during the course of the production of the light-sensitive materials and during storage after production and (c) that the sensitizing dyes are not left behind or decomposed after development into a colored matter to thereby stain the photographic materials.
Methods preventing the formation of stain caused by sensitizing dyes after development are known. Examples of these methods include a method wherein a carboxyalkyl group or a sulfoalkyl group is introduced as described in U.S. Pat. No. 2,519,001 and a method wherein a substituent group having a sulfonamido bond is introduced as described in U.S. Pat. No. 3,282,933. However, it is impossible that all of the above requirements for the sensitizing dyes can be completely met. For example, in the method described in U.S. Pat. No. 2,519,001, there is the possibility that high sensitivity is not obtained or a change in sensitivity occurs during storage after preparation. In the method described in U.S. Pat. No. 3,282,933, it is often impossible to reduce the degree of stain after processing to a desired level. When the spectral sensitivity distribution is longer than 540 nm, safelight fog is deteriorated to a greater extent under safelight conditions where ortho-sensitized photographic materials suitable for an argon laser are processed, and there is difficulty in achieving less safelight fog. Accordingly, a spectral sensitization technique which is highly sensitive to light of an argon laser which forms no or minimal residual color and which .allows photographic materials to be handled for a long time under an ortho safelight or a yellow safelight.